Overload device.



H. R. CANFIELD'.

OVERLOAD DEVICE.

APPLICATION FILED APR-19,1916.

1,293,697; Patented Feb. 11, 1919.

INVENTOR War/y FR Camf/e/c/ Z m @MZW All'y,

hiing and inspection.

HARRY P... GARFIELD, OF CLEVELAND, OHEO, ASSIGZEQI'L '1@ THE &MANUFACTURING COMPANY, OF CLEVELAND, OHIQ, CORPOMIIQZZ' @F GELIG.

ovnanonn nnvrcn.

Specification of Letters Batent.

Patented Felon ill, 1919..

Application filed April 19, 191%. Serial l lo. 88,281.

overload devices, and particularly to those having time-intervalfeatures.

The principal object of this invention is to provide an overload device,the operation of which is delayed for an interyal of time after theoccurrence of the overload, if the overload is'less than thepredetermined amount, and which, on excessively high or dangerousoverloads, operates instantaneously. Another object is to provide anoverload de'vicein which the time-interval elements are hermeticallysealed in a container to exclude dust, dirt, moisture, etc. Otherobjects will be apparent from the following specification.

lln the accompanying drawing, Figure l is a cross-sectional view of oneform of my invention; 2, a cross-sectional view showing a modificationthereof; and Fig. 3, a partial cross-sectional view or" anothermodification.

Referring to Fig. l, 11 is a winding energized by current in acontrolled circuit, not shown. it) is a main magnetic "frame containingthe winding ll and having a removable pole-piece 12 to facilitate assem-13 is a magnetic plunger which is attracted toward the polepiece 12 icymagnetic flux across the ap 14 when the winding 11 is energized, Thelower threaded end or" the plunger is screwed into the upper end of thehollow cylinder 15 oi preferably non-ma 1 etic material. The upper endof the p ung'er 13 may be hexagonal or square to receive a wrench. Bymeans of the flange 16 on the plunger and the packing washer 17 betweenthe flange and the cylinder 15, the cylinder is hermetically sealed whenthe plunger is screwed into it. The lower end of the cylinder 15 restson an adjustable pedestal 19 threaded into a bracket 20 attached to themagnetic frame 10, so that, by adjusting the pedestal, the length of theair-gap 14 may be varied. Within the cylinder 15 is the magnetic piston.21, immersed or partly immersed in a heavy liquid 22, such as mercuryor a heavy basic solution. The piston 21 is preferably cylindrical witha small clearance between its circumference and the wall of the cylinder15, and has the inter or cavity 23, in general cone-shaped terminatingat the-up or end in the smal onfice 36. Between tile piston 21 and theplunger 13 is another magnetic air-gap 30.

o The plunger 13carries the upwardly pro- ]ect1ng'stem 24 for engagingthe switcharm 25 to open the contacts 26 and 2?, which may therebyinterrupt the circuit including the wires 28 and 29 for controlling acircuitbreaker, not shown.

'The operation of the device shown on Fig. l is as follows: When anoverload of small or ordinary value occurs in the ding ll, flux isgenerated thereby in the n frame 10, the piston 21, the gap plunger; 13,the gap 1 2, and the ol This flux in the gap 1 2- exerts a pull on theplunger 13, and the i gap 30' exerts an upward pull on 21. The ilux inthe gap 14 is ins lift the plunger 13 and the der l5 and its contents,,0.- gap 30 is sufiicient to lift the pist moves slowly and uniforml illstraining action oi the liquid 22. upward movement of the piston cc toemerge from the liquid and to l portion of the liquid in the interic 23.The weight of this portion of balances the magnetic pull in the Lcausing the upward movement of the pistor 21 to cease. The air above thepiste then passes through the orifice 36, allow the level of the liquidin the cavity 23 to so slowly lowered. The weight of the liquidsupported by the piston 21 becoming less, the piston again movesupwardly. This action continues, resulting in a slow upward movement 0:5the piston 21, the rate dependmg upon the amount of magnetic pull in thegap 30 and the size of the orifice 36. The a movement of the piston 21is further steadied by the restricted flow of liquid and air downwardbetween. the piston and the wall of the cylinder. As the piston movesupward the magnetic reluctance of the gap 30 is gradually reduced, andmore and more fiux flows through the entire magnetic circuit. The pullon the piston 21 in the gap 30. therefore, increases and tends to socelerate the movement of the piston 21, but 1143 movement,

this tendency is counteractedfby so shaping the interior cavity 23 thatas the p ston moves upward the weightof the liquid lifted in a givenunit distance will ncrease with the upward movement of the pistonproportionately to the increase of magnetic pull, resulting in a uniformmovement of the piston. However, I do not limit my invention to anydefinite shape of this cav1t When the piston 21 has approximate yreached the plunger 13, the reluctance of the entire circuit has beendecreased sufficiently to 've suficient flux 1n the gap 14 to lift the punger 13, carryin with it the cylinder 15v and its contents, w ereuponthe stem 24 engages the arm controll ng circuit of thecircuit breaker,as described.

If the overload in the winding 11 is somewhat greater than that assumed1n the case will be eater and the piston 21 will travel upward y withreater rapidity, and before it has reached t e plunger 13, the fiux 1nthe gap 14 will lift the plunger 13 andopen the switch 25,andconsequently the circuit breaker. If, however, the overload in thewinding 11 is excessively high or dangerously large, the flux in the gap1 1 Wlll be sufiicient to lift the plunger 13 together with the cylinder15, the piston 21, and the liquid 22 at once without awaiting theindependent movement of the piston 21. The reater the current in thewinding 11, the aster w ll the piston move at any given point of its dueto its lifting a greater weight of liquid .a'nd to the greater rapiditywith which the air will flow through the orifice 36, and hence theshorter will be the time-interval between the overload and operation.

By adjusting the pedestal 19 the length of the gap 14 may be adjusted tochange the values of current in the coil 11 at which the device willoperate. It will be understood, of course, that the relative positionsof the plunger 13 and the piston 21 may be varied, as desired, byvarying the length of the cylinder 15. I

In the device shown in Fig. 2, an adjustable oleepiece 31 is provided tointroduce another gap 32 between the pole-piece 31 and the lower end ofthe piston 21. The pedestal 19 is in this case threaded in thepole-piece 31. y

In the operation of the device shown in Fig. 2, the current in thewinding 11 generates fiux in the magnetic frame 10, the adjustablepole-piece 31, the air-gap 32, the piston 21, the air-gap 30, theplunger 13, the air-gap14, and the pole-piece 12. The function of thegap 14 is the same as that described in connection with Fig. 1. The

' flux in the gaps 30 and 32 pull in opposite directions on the piston21" the fil X th 25, openingthe described, the fiux in the entirecircuit 7 gap 30 predominating, so that the piston 21 moves upwardly. Asthe upward movement of the piston, 21 decreams the reluctance in the gap30, it increases the reluctance in the gap 32, so that the flux in theentire circuit does not increase as rapidly as in the case of Fig. 1,and the movement of the piston 21 is not so rapidly accelerated. Thecompensating eilect of the hollow cavity in the iston 21 shown in Fig.1, ma be omitted, if desired, and the piston ma e solid. To steady themovement of the piston, any suitable liquid 22 may be used and a smallclearance allowed between the piston and the wall of the cylinder.

In Fig. 3 are shown the movable parts only of another form in which noliquid is used. The piston 21 is provided with the suction washer 33 andt e adjustable airport 34. A. downwardly-projecting guide 35, preferablynon-magnetic, is provided on the plunger 13 to centrally guide the iston21". When the flux in the gap 30 lifiis the piston 21, the air above thepiston moves through the port 34 and the space below the piston andretards the upward movement of the piston, the operation of the rest ofthe device being the same as of that shown in Fig. 1.

t is apparent from the foregoing that other means than that shown forretarding the upward movement of the magnetic piston 21 in the cylinder15 may be employed within the scope of my invention; that otheradjustment features may be employed; that the shape of the interiorcavity 23' of the piston 21 may be modified to control the rate ofmovement of the piston 21 as desired; and that other changes may be madewithout departing from the spirit of my invention.

I claim- 1. In an electromagnetic device, a winding, a casing and amagnetic member therein both influenced by current in the winding tomove when the current is above a predetermined value, and meansincluding means within the casing whereby the said movement of thecasing is delayed by a time interval inversely proportional to the rateof movement of the magnetic member.

2. In an electromagnetic device, a winding, a casing and a magneticmember therein both influenced by current in the winding to move whenthe current is above a predetermined value, and means including a fluidin the casing whereb the said movement of the casing is delaye by a timeinterval inversely proportional to the rate of movement of the magneticmember.

3. In an electromagnetic device, a winding, a casing and a magneticmember therein both influenced by current in the winding to move whenthe current is above a predetermined value, and'means including meanswithin the casing whereby the said movement of the casing is delayed bya time interval which is inversel proportional to the rate of movementof the magnetic member andwhich is decreased by an increase of currentin the winding.

4. In an electromagnetic device, a winding, a casin and a magneticmember therein both influenced by current in the winding to move. whenthe current is above a predetermined value, and means including a fluid'-i n the casing whereby the said movement of the casing is delayed by atime interval which is inversely proportional to the rate of movement ofthe magnetic member and which is decreased by an increase of current inthe winding.

5. In an electromagnetic device, a winding, a casing and a magneticmember therein both influenced by current in the winding to move whenthe current is above a predetermined value, means in the casing wherebythe said movement of the magnetic member is retarded, and the movementof the casing is delayed until after the movement of the magnetic memberexcept when the current is above a second higher predetermined value. 4

6. In an electromagnetic device, a winding, a casing and a magneticmember therein both influenced by current in the winding to move whenthe current is above a predetermined value, and means including a fluidin the casing whereby the said movement of the magnetic member isretarded, and the movement of the casing is delayed until after themovement of the magnetic member except when the current is above asecond higher predetermined value.

7. In an electromagnetic device, a mag- 40 netic circuit, a windingtherefor, a movable member in the circuit influenced by current in thewinding to move when the current is above a predetermined-value, andmeans for delaying the said movement of the member for a time intervalthe said means comprising a movable element in said magnetic circuithaving a dashpot connection with the said movable member 8. In anelectromagnetic switch, a mag- 5 netic circuit, a winding therefor, amovable member in the circuit influenced by current in the winding tomove when the current is above a predetermined value, means fordelayingthe said movement of the member for a time interval, the saidmeans comprising a movable element in the magnetic circuit hermeticallysealed within the movable member and movable relatively thereto, andmeans for retarding the relative movement.

9. In an electromagnetic switch, a mag netic circuit, a windingtherefor, a movable member in the circuit influenced by current in thewinding to move when the current is above a predetermined value, meansfor delaying the said movement of the member for a time interval exceptwhen the current is above a second predetermined value, the said meanscompnsing a movable element In the magnetic circuit hermetically sealedwithin the movable member and movable relatively thereto, and means forretarding the relative movement.

10. In an electromagnetic device, a magnetic circuit, a windingtherefor, a movable member and a movable element in the circuit bothinfluenced by current in the winding to move when the current is above apredetermined value, the movable member constituting a container-for themovable element, and means whereby the said movement of the movablemember is delayed until the reluctance of the circuit has been reducedby the movement of the element except when the current is above a secondpredetermined value.

11. In an electromagnetic device, a winding therefor, two movablemembers forming the two elements of a dashpot and both influenced bycurrent in the Winding to movewhen the current is above a predeterminedvalue, and means including a magnetic circuit of variable reluctance,whereby the said movement of one member is delayed until after the saidmovement of the other except when the current is above a secondpredetermined value.

12. In an electromagnetic device, a magnetic circuit, a windingtherefor, and two movable members in the circuit both influenced bycurrent in the winding to move when the current is above a predeterminedvalue, the two members forming the two elements of a dashpot, and meanswhereby the said movement of one member is delayed 10 until thereluctance of the circuit has been reduced by the said movement of theother members, except when the current is above a'second predeterminedvalue. v

13. In an electromagnetic device, a winding therefor, a movable memberinfluenced by current in the winding to move when the current is above apredetermined value, the movable member having a chamber movabletherewith and a movable magnetic element in the chamber, having adashpot connection with the chamber, and means including a magneticcircuit, the reluctance of which varies on the movement of the movableelement, whereby the movement of the member is delayed until after themovement of the element, except when the current is above a secondpredetermined value.

14. In an electromagnetic device, a magnetic circuit, a windingtherefor, a movable member in the circuit influenced by current in thewinding to move when the current is above a predetermined value, themember having a hermetically sealed chamber movable therewith, amagnetic element of the 189 magnetic circuit in the chamber, and meanswhereby the said movement of the member is delayed until after themovement of the element except when the current is above a secondpredetermined value. Q 15. In an electromagnetic device, a winding, amovable chamber-member influenced by current in the winding to move whenthe current is above a predetermined value only, and means for 'delayingthe movement of the chambef-member for a time interval, the said meanscomprising a movable element hermetically sealed within thechambermember. s q

16. In an electromagnetic device, a magnetic circuit, an energizingwinding, a member adapted to be moved upwardly by the magnetic influenceof the winding, and

means for retarding the movement of the member, comprising a body ofliquid in which the member is positioned, the said member having thereina cavity communinetic circuit, an energizing winding, a wor ing gap inthe circuit, a member adapted to be moved upwardly by theforce ofmagnetic flux in the gap, the force increasing with the movement ofthemember, means or retarding the movement of the member, com prising abody of liquid in which the member is positioned, the said member havingtherein an upwardly tapering cavity communicating below with the liquidand having a restricted orifice above, the sha e of the cavity and thesize of the orifice eing such that the weight of the member and theoccluded liquid balances the variable magnetic pull during the upwardmovement of the member.

Signed at Cleveland, Ohio, this 14th day of April, A.

HARRY R. OANFIELD.

